The present invention relates generally to spacecraft engineering and design. More particularly, the present invention relates to thermal control of spacecraft by cooling the spacecraft and its components utilizing transfer of propellant between satlets.
Recently, spacecraft have been designed by combining homogeneous cells, also referred to herein as satlets. The term “satlet” refers to a cell of a cell-based spacecraft where each satlet possesses the traditional architecture of a spacecraft including structure, power, fuel, attitude control and determination, spacecraft processing, etc. Thus, preferably each satlet has its own frame that incorporates multiple spacecraft subsystems including solar panels, batteries, one or more actuator wheels (functioning as a momentum wheel and/or reaction wheel), image sensors, thermal control systems, propulsion system including a fuel tank and thrusters, and electronics for command and data handling, data sharing, attitude control, and position control. Preferably, each satlet is substantially identical so as to be manufactured inexpensively and quickly. The satlets are aggregated together to form a single geographically co-located spacecraft which can seriously increase performance with increased numbers to support payload functions such as communications and surveillance.
Current spacecraft and launch vehicle interfaces employ various electrical connectors and separation systems including pyrotechnically actuated clamp bands, separation nuts, and separation bolts. The spacecraft reconfigurable satlet concept requires that satlets be interconnected by structural, fluid and electrical connectors. Structural, fluid and electrical connectors are often combined to create an “interface” connection. The interface must be capable of transferring structural loads between the two structures. The loads may include vibration, acceleration, thermal conduction, and static loads. For example, U.S. Patent Application Publication No. 2002/0164204 describes a spacecraft interface structure for mechanically connecting various spacecraft components including a spacecraft to a launch vehicle. Furthermore, U.S. patent application Ser. No. 14/444,092 filed Jul. 28, 2014, the disclosure of which is incorporated herein by reference, describes an improved interface connector capable for use to transfer power, data and fluid between satlets.
Moreover, thermal control of spacecraft is an important issue. Each satlet includes one or more electronic components for data processing and spacecraft control. These electronic components produce heat resulting in the need for thermal control. In current spacecraft, heat pipes and external radiators have been used to cool the electronic components. However, the smaller surface area and volume of satlets are not ideal for including heat pipes and external radiators.
Thus, it would be desirable to provide an improved method of cooling satlets and their electronics components.
Moreover, there is a need for an improved method of cooling satlets that does not require heavy and voluminous heat pipes and radiators.